Modifying Effects of Wealth on the Response to Nutrient Supplementation in Pregnancy on Birth Weight, Duration of Gestation, and Perinatal Mortality in Rural Western China: Double-Blind Cluster Randomized Controlled Trial

Abstract

It has been suggested that neonatal outcomes may differ between pregnant women from poor households and wealthier households receiving nutrient supplementation. A cluster randomized controlled trial found significantly lower dietary intakes of iron (as well as other micronutrients) among pregnant women in rural China from poor households than among those from wealthy households. Antenatal treatment with both iron/folic acid and multiple micronutrient (MMN) supplementation compared with folic acid alone was associated with increased duration of gestation, reduced early preterm delivery (<34 weeks of gestation), and significant reduction in early neonatal mortality. This study investigated the role of differences in household wealth on the effects of antenatal micronutrient supplements on birth anthropometry, duration of gestation, and perinatal mortality. Data were obtained from secondary analysis of a previously published cluster randomized controlled trial conducted in rural China on women during pregnancy, which examined the impact of iron/folic acid and MMN supplements compared with folic acid alone on several maternal/fetal outcomes. A total of 5828 eligible pregnant women were randomized to receive daily supplementation with folic acid (control), iron/folic acid, or MMNs until delivery. Ownership of household assets or facilities was used to construct a wealth index to indicate the poorest, middle, and the wealthiest households. Compared with folic acid, MMN supplementation in pregnant women from the 4 households was associated with a 68-g increase in birth weight (95% confidence interval [CI], 4–131; P < 0.037), a 60% reduction in low birth weight (relative risks [RR], 0.40; 95% CI, 0.21–0.78; P < 0.007), and a tendency toward 52% reduction in early neonatal mortality (RR, 0.48; 95% CI, 0.17–1.36). In comparison with folic acid, women from the poorest households receiving iron/folic acid supplements had a 90% reduction in the risk of early neonatal mortality (RR, 0.10; 95% CI, 0.01–0.79), an increase in duration of gestation by 0.41 weeks (95% CI, 0.18–0.65), and a 45% reduction in preterm birth (RR, 0.55; 95% CI, 0.32–0.93). In contrast, neither iron/folic acid nor MMN supplements had significant effects in women from wealthier households. These findings show that antenatal micronutrient supplementation is associated with a significant improvement in perinatal outcomes among pregnant Chinese women from the poorest households, but not among those from the wealthiest households.